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In 1971, a 27-year-old, 456-pound man went to his local university department of medicine to get advice on how to lose weight. Their response was starting but simple: stop eating altogether. While most people would look aghast and think the doctors were nuts, this guy was desperate enough to give it a try. His results over the ensuing weeks were so dramatic that he decided to prolong the fasting deprivation—for more than a year! He ate nothing but vitamins, noncaloric fluids, and yeast for a whopping 382 days. He lost 276 pounds and gained himself a spot in the Guinness Book of World Records. What’s more, he did so with no ill health effects. When the doctors checked back in on him five years later, he had gained back only about 15 pounds.

Although parts of the report seem unbelievable, and the period of fasting is obviously extreme, this dramatic anecdote highlights a very important point. Sometimes, extreme situations call for extreme actions. If you are obese and are suffering from any of the many obesity associated diseases, I can assure you that extreme measures are warranted. It also helps us refine the definition of what “extreme” is when talking about weight loss. Cutting out a piece of your stomach and stretch of large intestines is no longer considered extreme but I would argue it is far more risky than not eating for a year.

Types of intermittent fasting diets:

Alternate-day fasting: Subjects eat every other day. For humans, non eating days typically consist of one small meal of around 500 calories, amounting to a dietary energy reduction of approximately 65 percent to 80 percent.

5:2 diet: A person eats five days of the week and abstains from eating the other two (for example eating on Monday, Wednesday, Friday, Saturday, and Sunday and fasting on Tuesday and Thursday)—save for one small, 500-calorie meal on fasting days (cutting dietary energy by about 65 percent to 80 percent on those days).

Periodic fasting: This fast is undertaken anywhere from once a month to once a year. For a period of at least five days, food is avoided or subjects eat a modified “fasting-mimicking diet” that steps down energy intake over the fasting period and is low in carbohydrates, proteins, and calories.

Time-restricted feeding: Calories are not restricted, and dietary composition is not altered. But eating is confined to a window of typically 8, 10, or 12 hours per day.

The Evidence:

Since I strive for bringing you information regarding weight loss that is supported by evidence and not just hype, lets discuss the science behind fasting.

The theory that drives this diet technique is the fact that for the vast majority of human history humans did not have access to food on a daily basis. Food intake came in spurts brought in by the hunt or harvest but would be punctuated by periods of abstincen. It is only in recent history that there has been an abundant and never ending supply of food available to us cheaply and easily all day long. The idea behind intermittent fasting is that our bodies evolved in the environment of scarcity and are therefore ill equipped to deal with a constant intake of calories. By restoring what would be a more natural pattern of intake we can avoid all the metabolic derangements caused by daily over eating.

This certainly sounds like many of the other fads that have a seemingly plausible theoretical foundation but no real scientific support (e.g. paleo). As the body of scientific literature around fasting has grown, results have been cherry-picked and molded into fad diets that promise weight loss, increased energy, better sleep, and a variety of other benefits to human adherents—some with more evidential backing than others. As books of dubious scientific merit extolling the virtues of fasting fill the shelves, serious researchers continue to probe the genetic, immunologic, and metabolic dynamics that occur in fasting animals to separate hype from reality. There happens to be a tremendous amount of research showing the potential for significant health benefits to this pattern of eating.

I recently reviewed a synopsis of the data at this point from a journal called “The Scientist” and I encourage you to read the article in its entirety by clicking here. To summarize evidence suggests that intermittent fasting causes significant changes to various organs and tissue types. The fasting signal likely starts in the liver, the body’s central command for metabolism and then spreads throughout the body, from the brain and visceral fat to the muscles and more. There is evidence for improvements in immune function, cognitive function, and healing. Mostly, there is evidence for robust and sustained weight loss.

There are caveats, however.

As is the case with most of these types of scientific endeavors most of the data comes from animals, namely rodents. The benefits may not extend to humans or other animals. What human data there is is pretty sparse and certainly inconclusive.

It may be that the benefits of intermittent fasting are not from the fasting itself but from the calorie restriction which ensues. This would mean that any diet which restricts calories would be just as good as one that involves intermittent fasting.

Like any diet, if you stop doing it, the benefits are likely not to persist and you will gain the weight back (Click here for more on this topic).

With that said, I think that there are many reasons why intermittent fasting is worth trying if you have struggle with weight for a long period of time and have been unsuccessful with other forms of dieting.

The program is simple to understand. This is much simpler then trying to find a complicated diet were you have to adjust the types and quantities of food. There is no special shopping, calorie or point counting, or weighing of food.

The extremeness of the diet I think is an advantage. It is my opinion that part of the reason people are unsuccessful at weight loss is that they do not recognize the damage the weight does to their body until it is too late. By forcing someone to take such extreme steps it helps them put the dangers of the excess weight in perspective.

Anecdotally, it seems to really work.

It can’t hurt.

That last reason I think is the most important. The dangers and damage of being overweight are extreme and warrant trying any and everything that may help. Hopefully there will be more human data that shed more light on the effectiveness of intermittent fasting but until that time I think it is worth a shot.

If you have tried an intermittent fasting regimen please describe your experiences in the comments section below. Good luck!